Collaborative Research: CMG: Magnetohydrodynamics (MHD) Turbulence and the Geo-Dynamo: Lagrangian Averaging and Direct Numerical Simulations (DNS)

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Magnetic fields are a conspicuous feature of the ionospheres and magnetospheres of planets, including Earth, though their origin (the dynamo problem) is not well understood. This project is a theoretical investigation of magnetohydrodynamic (MHD) turbulence, or turbulent flow in the presence of magnetic fields. High resolution numerical simulations will be employed, and will be used to evaluate a method of simplifying turbulence processes called the Lagrangian-averaged (or "alpha") model. When validated, the method will be applied to MHD regimes relevant to the geodynamo (so-called low magnetic Prandtl number regimes) that have not been modeled previously. The work will not only advance the understanding of the geodynamo but will be a test of the alpha model, which has been proposed for other investigations of turbulent flow. The project provides for training graduate students and a postdoctoral research associate, and will sponsor an international workshop at NCAR on the modeling of complex geophysical flows in the summer of 2006. The grant is funded jointly by the Division of Atmospheric Sciences and the Division of Mathematical Sciences through the NSF program, Collaborations in Mathematical Geosciences (CMG).